System and method for providing differentiated services

ABSTRACT

The present invention relates to a method and arrangements for updating the mapping of traffic in the form of a set of service level aggregate flows (SLS 1 , SLSM) to a set of partial resources (B 1 , BN) for forwarding the traffic in a communications network ( 21 ). Each service level aggregate flow corresponds to a service level associated with a set of service requirements. Information regarding traffic characteristics of each service level aggregate flow and performance of the set of network resources are obtained. Based on this information, the mapping of the set of service level aggregate flows to the set of network resources is updated to achieve a more efficient utilization of the set of network resources, while fulfilling the set of service requirements.

FIELD OF THE INVENTION

The present invention relates to communications systems and methods, andmore particularly, to systems and methods for providing differentiatedservices to flows of telecommunications traffic in a resource efficientmanner.

BACKGROUND OF THE INVENTION

The Internet is a packet based network transporting many different typesof telecommunications traffic, such as voice, data, and multimediatraffic, which originates from a large variety of applications.Different types of traffic have different quality of service (QoS)demands. For voice traffic a small and uniform packet delay isparticularly important, while small packet loss is the most importantrequirement for data traffic. Furthermore, service providers areinterested in offering services with different QoS that allow them tosatisfy the varying needs of their customers and to maintain adifferentiated pricing scheme. Therefore several mechanisms forproviding different QoS to different users and traffic flows in packetbased networks such as the Internet have been developed.

The international patent application WO02/25867 describes a radio accessnetwork that provides different priority classes to different packetdata connections with a user equipment. The priority class of a dataconnection may be dynamically adjusted by a control node in accordancewith a throughput criterion which is communicated to the control node bythe user equipment.

The IETF (Internet Engineering Task Force) has developed the IntegratedServices (IntServ) architecture which is described in IETF RFC 1633. TheIntServ architecture uses an explicit mechanism to signal per-flow QoSrequirements to network elements such as hosts and routers. There are anumber of drawbacks associated with IntServ. IntServ requiresmaintenance and control of per-flow states and classification. Networkresources are reserved on a per-flow basis which introduces scalabilityproblems at the core networks where the number of processed flows oftenis in the range of millions. Therefore it is only practical to use theIntServ architecture in small access networks where the number of flowsis modest.

To overcome the scalability and complexity problems of IntServ the IETFintroduced the Differentiated Services (DiffServ) architecture,described in IETF RFC 2475. Traffic through network core routersimplementing DiffServ is treated on an aggregate basis. Traffic enteringa network is classified and assigned to different behaviour aggregates.Each behaviour aggregate is identified by a single DS (DifferentiatedServices) codepoint. When the traffic is classified packets are markedwith a particular DS codepoint which is placed in a DS field in the IP(Internet Protocol) header. Within the core of the network, a packet isforwarded according to a per-hop behaviour (PHB) associated with the DScodepoint of the packet. A PHB determines the externally observableforwarding behaviour (such as forwarding delay and packet loss) of anode at different load levels. PHBs are logical network resources thatgovern the use of underlying physical network resources. Thus a PHB canbe seen as a partial network resource, which defines a subset of a totalnetwork resource.

The international patent application WO02/11461 is one example of adocument that describes a DiffServ system. It discloses a method andarrangement for providing dynamic quality of service by means of abandwidth broker in an IP Network that includes a DiffServ architecture.The bandwidth broker may obtain resource availability information bycommunication only with border routers of a DiffServ domain.

Another example of a document that discusses a DiffServ implementationis the international patent application WO02/080013, which describesdynamic resource allocation that provide differentiated services over abroadband communication network that includes a satellite.

When a service provider sells a bearer service to an end user theservice is usually specified. The service may be specified by a ServiceLevel Specification (SLS) that includes QoS requirements for theservice. Thus SLSs may be used to define different classes or levels ofservice. In order to fulfil the QoS requirements of the SLS theallocation of resources assigned to the traffic associated with the SLSis crucial. Today the mapping of SLSs to network resources is usuallymade semi-permanently as part of the provisioning and configuration of anetwork, see IETF RFC 3086. The mapping is set up to suit an expectedmix of traffic.

In traditional networks, the traffic characteristics are fairly wellknown. In future multi-service networks and multi-access networks,traffic characteristics will be dynamic due to changes in userbehaviour, introduction of new applications, etc. Moreover, thesechanges imply that the network must be flexible in terms of resourceallocation to different QoS classes. New techniques for managingnetworks efficiently will therefore be needed.

SUMMARY OF THE INVENTION

As mentioned above networks of today are dimensioned according to acertain expected traffic mix. The network elements and mechanisms arethen statically configured via management interfaces. If the traffic mixchanges a substantial effort is needed to reconfigure the network. Thiswill often be more costly than to let the network operate with asuboptimal configuration. In networks with highly dynamic traffic mixesit would thus be possible to improve network resource utilizationconsiderably if mappings of service levels to network resources could bechanged easier and on a timescale that is much shorter than what iscommon today.

An object of the present invention is thus to provide arrangements and amethod that allows for dynamic mapping of service levels to networkresources such that efficient resource utilization may be achieved evenwhen the traffic mix varies.

The above stated object is achieved by means of a system according toclaim 1, a method according to claim 11 and a control unit according toclaim 20.

The arrangements and methods according to the present invention makes itpossible to dynamically and automatically change the mapping of trafficto partial resources based on information about the actual traffic mixcurrently being transported in the network. The mapping is adapted tothe traffic mix to obtain a mapping that achieves a more efficientutilization of resources in total when forwarding the traffic mix, whilefulfillng the service requirements that have been set up. The optimalmapping is usually considered to be the mapping that minimizes theamount of wasted resources, i.e. resources that is not used forforwarding the traffic mix but which is reserved in such a way that itcannot be used for transporting other traffic.

According to a first aspect of the present invention a system isprovided for forwarding telecommunication traffic of a number ofmicroflows in a quality of service enabled telecommunications network.Each microflow is allocated a service level from a set of predeterminedservice levels to create a set of service level aggregate flows and eachservice level is associated with a set of service requirements. Thesystem comprises a set of partial resources for forwarding the trafficin the network, to which resources the service level aggregate flows aremapped. The system further comprises a control unit arranged to receiveinformation regarding traffic characteristics of each service levelaggregate flow and resource performance and to update the mapping of theservice level aggregate flows to the set of partial resources, based onthe received information, to obtain an updated mapping that reduces thetotal amount of wasted resources, while fulfilling the servicerequirements of the service levels.

According to a second aspect of the present invention a method isprovided for updating a mapping of service level aggregate flows to aset of partial resources for forwarding traffic in a quality of serviceenabled telecommunications network. The method comprises the step ofreceiving a set of service level aggregate flows. Each service levelaggregate flow is made up of microflows that have been allocated thesame service level from a set of predetermined service levels and eachservice level is associated with a set of service requirements. Themethod also comprises the step of obtaining information regardingtraffic characteristics of each service level aggregate flow andresource performance, and the step of updating the mapping of theservice level aggregate flows to the set of partial resources, based onthe obtained information, to obtain an updated mapping that reduces thetotal amount of wasted resources, while fulfilling the servicerequirements of the service levels.

According to a third aspect of the present invention a control unit isprovided for controlling the mapping of service level aggregate flows oftelecommunications traffic to a set of partial resources for forwardingtraffic in a network. Each service level aggregate flow corresponds to aservice level associated with a set of service requirements. The controlunit comprises means for receiving information regarding trafficcharacteristics of each service level aggregate flow and the performanceof the set of partial resources. Furthermore the control unit comprisesmeans for dynamically controlling the mapping of the service levelaggregate flows to the set of partial resources, based on the receivedinformation, to obtain an updated mapping that reduces the total amountof wasted resources, while fulfilling the service requirements of theservice levels.

According to a preferred embodiment of the invention resource parametersthat govern the performance of the partial resources are updated in viewof the current traffic mix to achieve the combination of resourceparameters and mapping that gives the most efficient utilization of thepartial resources, which is the mapping that minimizes the total amountof wasted resources and still fulfils the service requirements of theservice levels.

To optimize the utilization of resources of a network with severalservice levels, the mapping of different service levels on the availablenetwork resources must be adapted to the current traffic mix in adynamic fashion. The present invention enables a network operator toperform adaptive mapping in a dynamic fashion, as opposed to thesemi-permanent configuration of this mapping that is done in state ofthe art products.

A semi-permanently performed mapping, as in the prior art solutions, maybecome inefficient if the traffic mix changes. The fact that the mappingis inefficient may not be detected and even if it is detected it isoften cumbersome to change the semi-permanently performed mapping.

In contrast it is an advantage of the present invention that it allowsfor continuous supervision of the current traffic mix and correspondingadaptation of the mapping. According to the present invention themapping may be adapted quickly and automatically when the traffic mixchanges.

The present invention makes it possible for a network operator toutilize his network resources more efficiently. Thereby the operator maybe able to forward more traffic, provide better quality of service orreduce the amount of network recourses.

Since the present invention allows for continuous supervision of thecurrent traffic mix and dynamic optimization of the mapping of servicelevels to network resources, the present invention can also make iteasier for a network operator to ascertain that the service requirementsof different service levels are fulfilled and that no network resourcesare overloaded without having to provide overcapacity of networkresources.

Further advantages and objects of embodiments of the present inventionwill become apparent when reading the following detailed description inconjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram illustrating a system wherein thepresent invention may be used.

FIG. 2 is a schematic block diagram illustrating an embodiment of amechanism for dynamic mapping between aggregate flows and partialresources according to the present invention.

FIG. 3 is a schematic block diagram illustrating a mechanism accordingto the present invention for dynamic mapping between aggregate flows andper hop behaviours (PHBs) in a network using the Differentiated Servicesarchitecture.

FIG. 4 is a schematic block diagram illustrating an alternativeembodiment of the mechanism illustrated in FIG. 3.

FIG. 5 is a schematic diagram illustrating a mapping of service levelaggregate flows to PHBs.

FIG. 6 is a schematic diagram illustrating how the mapping shown in FIG.5 may be changed according to the present invention in order to providefor more efficient utilization of resources.

DETAILED DESCRIPTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. In thedrawings, like numbers refer to like elements.

According to the present invention mappings of service levels toresources are changed dynamically and automatically, based on feedbackor signalling information giving information regarding the actualtraffic mix currently being transported in the network. The presentinvention may for instance be used for mapping UMTS bearer services ontoDiffServ PHBs.

The present invention is based on dynamic optimization of mapping andwill be explained in general by means of an illustration in FIG. 1. FIG.1 illustrates a number of packet flows being multiplexed on the samephysical link 31. The flows may be generated by for example telephony,video conferencing, streaming, and interactive applications. Thereforethe flows have different requirements on bandwidth, transport delay andpacket loss rate. Thus it is advantageous to treat the flows accordingto different service levels and to classify the traffic accordingly.Flows having the same or similar QoS requirements are allocated the sameservice level and are treated as an aggregate traffic flow in order toreduce complexity.

Assume that each packet flow has well defined requirements on bandwidth,delay and packet loss. In FIG. 1, the telephony application is denotedA1, the video conferencing application is denoted A2, etc. The trafficmix to be transported on the physical link 31 is made up of n1 flowsfrom application A1, n2 flows from application A2, etc. The flows fromapplication A1 are allocated a first service level having QoSrequirements R1 and form a service level aggregate flow S1, similarlythe flows from application A2 are allocated a second service levelhaving QoS requirements R2 and form a service level aggregate flow S2etc. However note that flows from different applications may be combinedinto a single aggregate flow if this is appropriate in view of the QoSrequirements of the flows.

To govern the admission of traffic onto the physical link a number ofbuffers B1, B2 . . . BN are set up. Each buffer is allocated a part ofthe bandwidth that is available on the physical link. Thus, the buffersrepresent a set of partial resources on which the traffic is to bedistributed. A mapping rule determines the mapping between the aggregateflows S1, S2 . . . SM and the partial resources B1, B2 . . . BN.Moreover a given multiplexing rule determines the scheduling of thetransmission on the link 31 of the packets belonging to each partialresource. The scheduling ascertains that the delay and loss targets foreach flow are fulfilled.

In order to achieve as efficient utilization of resources as possible itis desirable to make sure that the traffic transporting capabilities ofthe partial resources can be used to their fullest extent. This impliesthat traffic flows should be fed to the partial resources such that asmuch traffic as possible can be transported by the partial resources. Ifthe traffic transporting capability of a partial resource is notutilized as much as it could be in view of the current traffic mix, thepart of the partial resource that is not used for transporting trafficis a wasted resource. The term “wasted resources” is in thisspecification defined as resources that are not used for transporting agiven traffic mix but which are still reserved such that they are notavailable for transporting other traffic. The meaning of wastedresources will be explained further below in connection with theaccompanying drawings.

The optimal mapping could be defined as follows:

For a given traffic mix consisting of the aggregate flows S1 . . . SM,and for a given set of partial resources B1 . . . BN, the optimalmapping minimizes the wasted resources when transporting the traffic mixsuch that the requirements R1 . . . RM are fulfilled.

The network operator may choose an alternative definition of the optimalmapping, but usually the operator is interested in minimizing the amountof wasted resources that arise when transporting a given amount oftraffic while fulfilling QoS requirements associated with the traffic.Thereby the operator may be able to make some resources available fortransporting additional traffic.

If it is possible to vary parameters that are associated with thepartial resources and that have an impact on the performance of thepartial resources an even better utilization of partial resources couldbe obtained by determining the combination of mapping and resourceparameters that minimizes the wasted resources while fulfilling theservice level QoS requirements. Resource parameters that govern theperformance of the partial resources may for instance be the parameterssuch as buffer size and priorities assigned to different partialresources. Such parameters can affect the portion of an underlyingphysical resource that is allocated to the partial resource. The choiceof mechanism for scheduling the access of the partial resources to aphysical link also affects the performance of the partial resources. Theresource parameters may have an impact on the performance of the partialresources in such a way that they affect the packet delay and packetloss of the partial resources at different load levels. The ability toadapt the partial resources makes it possible to minimize the totalamount of network resources that is allocated for transporting a givenset of aggregate traffic flows.

Stated in the above-mentioned manner, there is a direct translationbetween the mapping and scheduling rules and the cost of transportingthe traffic mix. The optimal mapping is thus the mapping that minimizesthe bandwidth cost.

Different traffic mixes will have different optimal mapping andscheduling rules. This implies that the operator could reduce the costby changing the mapping or by changing both the mapping and schedulingrules dynamically as the traffic mix changes on a given link.

Obviously the above definition of the optimal mapping as the mappingthat minimizes the bandwidth cost corresponds to the definition of theoptimal mapping as the mapping that maximizes the operator's income.

FIG. 2 is a block diagram that illustrates an embodiment of a mechanismfor performing the dynamic optimization of the mapping and thescheduling rules according to the present invention. FIG. 2 shows Lmicroflows f1, f2, . . . , that arrives at a network node and requestaccess to a physical network element 21, such as a link. A microflow isa single instance of an application-to-application flow. The microflowsoriginate from different applications and have different requirements onQoS such as bandwidth, delay and packet loss. These requirements aresignalled to, and negotiated with, an admission control function 22.Provided that link resources are available, the admission controlfunction allocates a Service Level Specification (SLS) to a particularmicroflow. The Service Level Specification includes a TrafficConditioning Specification (TCS) that specifies traffic characteristics,such as peak rate, mean rate, and maximum allowed burstiness, that themicroflow must fulfil at the ingress of the network. The SLSs definedifferent service classes or levels and the microflows are allocatedSLSs that correspond to their respective QoS requirement. Flows havingthe same or similar QoS requirements are allocated the same SLS so thata number of aggregate traffic flows are formed. FIG. 2 shows M aggregateflows SLS1, . . . ,SLSM. Traffic parameters such as mean bandwidth andburstiness are measured by means of a measurement function 26 for eachaggregate flow separately. These parameters are, according to thepresent invention, reported to a mapping control unit 23 as feedbackinformation. The feedback information makes the mapping control unit 23aware of the characteristics of the actual traffic mix such as theamount of traffic of each aggregate flow and the ratio between thetraffic amounts of the different aggregate flows.

The mapping control unit 23 is responsible for programming a mappingfunction 24 based on the received feedback information. The mappingfunction 24 maps the aggregate flows to N partial resources B1, . . . ,BN, each having different QoS levels. The QoS level of a partialresource is determined by multiplexing rules or scheduling rules thatgovern how the partial resource is multiplexed onto the physicalresource. Thus different partial resources may be allowed to usedifferent portions of a total underlying physical resource. This may forinstance be governed by a Round Robin scheduling mechanism or othermechanism as is well known to the person skilled in the art.

In the embodiment shown in FIG. 2, the multiplexing of the partialresources is governed by a multiplexing function 25 which may bereprogrammed under the control of the mapping control unit 23. Thus thecapacity of the partial resources may be changed in response to thefeedback information regarding the traffic mix that the mapping controlunit receives. The mapping control unit may also receive feedbackinformation from a measurement function 27 regarding packet delay andloss data per partial resource. Thereby the mapping control unit maydetect if a partial resource is or is about to become overloaded whichfurther assists the mapping control unit in determining the optimalmapping and multiplexing rules. The feedback information from themeasurement function 27 may further give an indication about whether ornot the QoS requirements per microflow are fulfilled. The delay andpacket loss performance for the microflows on the network element mayalso be measured end to end and the result may be compared with thedelay and drop rate requirements for the flows as stated in the SLSs forthe microflows.

Using the above mentioned feedback information regarding trafficcharacteristics and resource load, as well as the comparisons of theactual QoS to the QoS requirements, the mapping control unit determinesthe optimal mapping and scheduling rules by means of an optimizationalgorithm. The optimal mapping and scheduling rules are, as mentionedabove, usually considered to be the mapping and scheduling rules thatminimizes the total amount of wasted resources and thereby alsominimizes the utilization of the network element 21. The feedbackinformation from the measurement functions 26 and 27 to the mappingcontrol unit allows the system to adapt in real-time to changes in thetraffic mix.

In the embodiment illustrated in FIG. 2 the characteristics of thepartial resources B1, . . . , BN may be varied by means of changing thescheduling rules. Thus the mapping control unit is able to affect theresource utilization both by controlling the scheduling rules, i.e. thecharacteristics of the recourses, and by controlling the mapping ofaggregate flows to the partial resources. Even if the scheduling rulesare fixed so that the characteristics of the partial resources cannot bevaried, the mapping may still be set to the mapping that is optimal inview of the available partial resources. However in a more flexiblesystem where it is possible to adapt the partial resources it is usuallypossible to obtain a more efficient utilization of the total resourcesthan in the less flexible system with fixed partial resources.

FIG. 3 illustrates an embodiment of the present invention in an IP QoSnetwork using the Differentiated Services QoS architecture. In thisarchitecture, the partial resources to which aggregate flows are mappedare called per hop behaviours (PHBs). In FIG. 3 it is illustrated thatthe aggregate flows SLS1, . . . , SLSM are mapped to the PHBs PHB1, . .. , PHBN. A PHB is an allocated buffering and link bandwidth resourcethat determines the externally observable forwarding behaviour (such asforwarding delay or packet loss) of a node. In the embodiment shown inFIG. 3, the mapping control unit controls the mapping of the aggregateflows to the PHBs in response to received feedback information from themeasurement functions 26 and 27. The PHBs are scheduled on a link 31 bya scheduling function 28. The scheduling function 28 is programmed bythe mapping control unit so that the PHBs may be optimized to thecurrently received traffic mix.

In the embodiments of the present invention shown in FIGS. 2 and 3traffic parameters of the aggregate flows SLS1, . . . ,SLSM are measuredby the measurement function and reported to the mapping control unit.The mapping control unit is thereby provided with information regardingthe traffic characteristics of the aggregate flows which is used todetermine the optimal mapping in view of the traffic mix. According toan alternative embodiment of the present invention, the informationregarding traffic characteristics that is reported to the mappingcontrol unit is based on calculations instead of measurements. Duringthe set up of a microflow it may be determined that a certain microflowmay not exceed certain traffic limits e.g. with respect of mean rate andpeak rate. These traffic limits may be reported to the admission controlfunction 22 by means of RSVP or ATM signalling. The admission controlfunction 22 may then calculate corresponding traffic limits peraggregate flow based on the traffic limits of the microflows included inthe respective aggregate flow. The calculated traffic limits peraggregate flow may then be reported from the admission control function22 to the mapping control unit 23 as information regarding the trafficcharacteristics of the aggregate flows. According to this alternativeembodiment of the present invention the measurement function 26 may thusbe omitted as is indicated in FIG. 4. Alternatively the measurementfunction 26 may be arranged such that it can receive traffic limitcalculations from the admission control unit and can be set to reporteither measurements or received traffic limit calculations to themapping control unit 23.

If the information regarding the traffic characteristics of theaggregate flows that is reported to the mapping control unit is based oncalculated traffic limits, the mapping will probably be adapted totraffic amounts that are somewhat overestimated, since the microflowsmay be below set-up traffic limits but not above. It may thus likelythat mappings based on measured information about the traffic mixusually are more resource-efficient than mappings based on calculatedinformation.

To further explain the function of the system according to the inventionfor controlling the utilization of partial resources, a concrete andsimplistic example of an optimization algorithm that may be used by themapping control unit will be explained below with reference to FIGS. 5and 6.

FIG. 5 illustrates the optimization principle for an example where sevenservice level aggregate flows SLS1, SLS2, . . . , SLS7 are mapped onthree PHBs PHB1, PHB2, PHB3. Each PHB has underlying physical resourcesallocated to it in terms of two parameters: peak rate and mean rate.Likewise, each service level aggregate flow is associated withrequirements on peak rate and mean rate. In FIG. 5, the peak rate isindicated on the x-axis, while the ratio between the mean rate and thepeak rate is indicated on the y-axis. The mean rate is thus the area ofa PHB box or aggregate flow box. In this example, all service levelaggregate flows that are mapped to a specific PHB have the sametime-scale of the peak rate bursts, and this time-scale is matched tothe buffer size of the PHB.

If the ratio between the mean rate and peak rate is one, the PHBresources are allocated to transport the peak rate of the traffic. Nopacket loss or queuing delay will then occur. If the ratio is less thanone, the operator has sold more peak rate service level specificationsthan the network can handle instantaneously. Traffic must therefore bebuffered. As a result, queuing delay and even packet loss may occur.

The diagram in FIG. 5 gives an illustration of the optimization problemas a problem of packing aggregate flow boxes SLS1, . . . ,SLS7 into PHBboxes PHB1, PHB2, PHB3 in the most efficient manner. When the aggregateflow boxes SLS1, . . . , SLS7 stay within the limits of a PHB box, theunderlying physical resources of the PHB can support the requirements ofthe aggregate flows in terms of peak rate and mean rate. The area of aPHB box not covered by aggregate flow boxes indicates wasted mean rateresources.

The optimization algorithm according to an embodiment of the presentinvention minimizes the waste of mean rate resources by moving theborders between the PHB boxes along the x-axis, and by adjusting theheight of the PHB boxes so that it equals the height of the highestaggregate flow within the box. This is indicated in FIG. 6, where theboundary between the PHB1 and PHB2 boxes has been moved to the left, andthe height of these two boxes have been adjusted to the highestaggregate flow within each box. The adjusted PHB boxes are labelledPHB1+ and PHB2+ in FIG. 6.

As can be seen, the waste of resources has been decreased within thePHB1+ box compared to PHB1. On the other hand, the waste of resourceshas increased somewhat within the PHB2+ box compared to PHB2. However,the decrease of waste is higher than the increase, resulting in a netsaving of resources.

The optimization algorithm is related to the mapping function 24 and thescheduling function 28 of FIG. 3 as follows. Moving the border of a PHBbox along the x-axis implies that the mapping of the aggregate flowsonto PHBs must be changed. This is accomplished by re-programming themapping function 24. Moreover, the buffering and bandwidth resources ofa PHB are adapted when the border of a PHB box is moved along the x- ory-axis. This is accomplished by re-programming the scheduling function28.

For the special case with two PHB boxes, the aggregate flow boxes haveequal widths and their heights represent a geometrically decreasingsequence {a_(i)}, the following optimization algorithm can be used forrecursively updating the mapping of service level aggregate flows to thetwo PHB boxes:(a ₁ −a _(T+)1)/(a _(T)+1−a _(T+)2)<(M−T−1)=>T:=T+1(a ₁ −a _(T))/(a _(T) −a _(T+)1)>(M−T)=>T:T−1

M is the total number of service level aggregate flows and T is thenumber of service level aggregate flows in the first of the two PHBboxes. The algorithm simply states the condition under which the T:thservice level aggregate flow, i.e. SLST, should be moved from the firstPHB to the second PHB, or the T+1:th service level aggregate flow, i.e.SLST+1, should be moved from the second PHB to the first PHB.

After a service level aggregate flow has been moved, the resources ofthe PHBs must be adapted accordingly. This adaptation can be calculatedbased on a priori knowledge of the resource requirements of the servicelevel aggregate flows, or be based on measurements of the PHBperformance in terms of delay and packet loss.

The two-dimensional optimization algorithm outlined here can begeneralized to a multi-dimensional case including additional parametersto describe traffic and resources, such as various leaky bucketparameters. However, it is likely that a nice recursive algorithm thatfinds the global optimum does not exist for the general case.

The most straight forward approach is to calculate the amount of wastedresources for all possible, mappings of service level aggregate flows onPHBs, and pick the best. To reduce the number of combinations, theservice level aggregate flows should be grouped according to theirsimilarity in terms of resource requirements, just as in the case shownin FIG. 5.

In the above-described algorithm each service level aggregate flow ismapped on a single PHB. However according to an alternative embodimentof the present invention a service level aggregate flow may be splitbetween two or more resources, such as PHBs. Splitting a service levelaggregate flow between several resources may lead to even more efficientutilization of resources in some cases. It may be particularlyadvantageous in cases where it, for some reason, is not allowed orpossible to adapt the characteristics of the resources.

In cases where the traffic mix changes often, the above mentionedalgorithm may have the effect that the mapping is changed veryfrequently. Moving service level aggregate flows back and forth betweendifferent PHBs several times during a short time period may havenegative effects on the network performance. To overcome such negativeeffects an algorithm involving some kind of hysteresis may be used. Aservice level aggregate flow may for instance be moved from one PHB toanother only when the decrease in wasted resources is above a certainlimit or there may be a specified minimum period of time between twoconsecutive rearrangements of the mapping of service level aggregateflows to resources.

A change of the traffic mix will result in that the characteristics ofthe service level aggregate flows changes. In FIGS. 5 and 6 this willhave the effect that the areas of the boxes SLS1, . . . , SLS7 changes.After such a change it may be advantageous to rearrange the mapping ofaggregate flows to partial resources in order to achieve a moreefficient utilization of total resources. Since the mapping control unitaccording to the present invention receives information regarding thecurrently received traffic mix the present invention makes it possibleto quickly detect and adapt to changes in the traffic mix.

The information from the measurement function 26 or the admissioncontrol function 22 may include information regarding such trafficcharacteristics of the service level aggregate flows as the mean rate,peak rate and/or some other characteristic.

The information regarding the current traffic mix, which according tothe present invention is measured or calculated and reported to themapping control unit, may be used for other purposes than optimizing theutilization of resources. It may also be used to determine parametersfor optimizing the performance of QoS mechanisms implemented in routers.There are e.g. implementations of the DiffServ architecture where it isimportant to configure the expected mean length of packets. If whenmeasuring the traffic in the measurement function 26, significantchanges in the mean packet length can be detected, this informationcould of course be used to change the DiffServ configuration parameters.

The mapping control unit is a central unit of the present invention. Itis responsible for ascertaining that the partial resources are used inan efficient manner in accordance with the currently received trafficmix without being overloaded. Several different implementations of themapping control unit are possible as will be apparent to the personskilled in the art. It is for instance possible that each node of anetwork or QoS domain is provided with a mapping control unit, or themapping control unit may be provided in a centralized control node thatcommunicates with the network nodes. It win be apparent to the personskilled in the art how the mapping control unit and other functions ofthe present invention may be implemented using known hardware andsoftware means. The mapping function 24 is according to the presentinvention implemented to be programmable under the control of themapping control unit. The easiest way of implementing the programmablemapping function may be by means of software means, but programmablehardware implementations are also possible as well as implementations ofcombinations of hardware and software. As mentioned above, it is apreferred feature of the present invention that the multiplexingfunction 25 or scheduling function 28 also is programmable under thecontrol of the mapping control unit.

In the drawings and specification, there have been disclosed typicalpreferred embodiments of the invention and, although specific terms areemployed, they are used in a generic and descriptive sense only and notfor purposes of limitation, the scope of the invention being set forthin the following claims.

1-28. (canceled)
 29. A system for forwarding telecommunication trafficof a number of microflows in a quality of service enabledtelecommunications network, each microflow being allocated a servicelevel from a set of predetermined service levels to create a set ofservice level aggregate flows, wherein each service level is associatedwith a set of service requirements, said system comprising a set ofpartial resources for forwarding the traffic in the network, to whichpartial resources said service level aggregate flows are mapped, saidsystem further comprising a control unit arranged to receive informationregarding traffic characteristics of each service level aggregate flowand resource performance; and to update the mapping of the service levelaggregate flows to the set of partial resources, based on said receivedinformation, to obtain an updated mapping that reduces the total amountof wasted resources, while fulfilling the service requirements of theservice levels, wherein the control unit furthermore is arranged toupdate resource parameters governing the performance of the set ofpartial resources to achieve the combination of mapping and resourceparameters that minimizes the total amount of wasted resources, whilefulfilling the service requirements of the service levels.
 30. Thesystem of claim 29 wherein said resource parameters are schedulingparameters governing how the set of partial resources are multiplexed ona physical link.
 31. The system of claim 29 wherein the set of partialresources is a set of DiffServ per hop behaviors.
 32. The system ofclaim 29 further comprising a resource performance measuring functionfor measuring resource performance and reporting measurement results tothe control unit, and said information regarding resource performance isInformation about packet delay and packet loss of each partial resourcemeasured by said resource performance measuring function.
 33. The systemof claim 29 further comprising a traffic measuring function formeasuring traffic characteristics of at least one service levelaggregate flow and reporting measurement results to the control unit,and at least a portion of said information regarding trafficcharacteristics of each service level aggregate flow is informationabout mean rate and peak rate measured by said traffic measuringfunction.
 34. The system of claim 29 wherein said system furtherincludes means for receiving signalling information concerning trafficlimits set up for the microflows, means for calculating correspondingtraffic limits per service level aggregate flow based on the signallinginformation concerning traffic limits per microflow and means forsending the traffic limits per service level aggregate flow to saidcontrol unit as at least a portion of said information regarding trafficcharacteristics of each service level aggregate flow.
 35. The system ofclaim 29 wherein the control unit is arranged to map each service levelaggregate flow to one or several partial resources in the set of partialresources.
 36. The system of claim 29 wherein the control unit isarranged to use a recursive optimization algorithm for minimizing thetotal amount of wasted resources in view of the received information andthe set of service requirements.
 37. The system of claim 29 wherein thecontrol unit is arranged to update the mapping when the receivedinformation indicates that at least one traffic characteristic of atleast one service level aggregate flow has changed by a predeterminedamount since the last update of the mapping.
 38. A method for updating amapping of service level aggregate flows to a set of partial resourcesfor forwarding traffic in a quality of service enabledtelecommunications network, comprising the step of receiving a set ofservice level aggregate flows, wherein each service level aggregate flowis made up of microflows that have been allocated the same service levelfrom a set of predetermined service levels, each service level beingassociated with a set of service requirements, further comprising:obtaining information regarding traffic characteristics of each servicelevel aggregate flow and resource performance; and updating the mappingof the service level aggregate flows to the set of partial resources,based on said obtained information, to obtain an updated mapping thatreduces the total amount of wasted resources, while fulfilling theservice requirements of the service levels, wherein the step of updatingthe mapping includes updating resource parameters governing theperformance of the set of partial resources to achieve the combinationof mapping and resource parameters that minimizes the total amount ofwasted resources, while fulfilling the service requirements of theservice levels.
 39. The method of claim 38 wherein said resourceparameters are scheduling parameters governing how the set of partialresources are multiplexed on a physical link.
 40. The method of claim 38wherein the step of obtaining information includes measuring packetdelay and packet loss of each partial resource.
 41. The method of claim38 wherein the step of obtaining information includes measuring meanrate and peak rate of at least one service level aggregate flow.
 42. Themethod of claim 38 wherein said step of obtaining said informationregarding traffic characteristics of each service level aggregate flowincludes the step of receiving signalling information concerning trafficlimits set up for the microflows and the step of calculatingcorresponding traffic limits per service level aggregate flow based onthe signalling information concerning traffic limits per microflow toform at least a portion of said information regarding trafficcharacteristics of each service level aggregate flow.
 43. The method ofclaim 38 wherein the mapping is updated such that each service levelaggregate flow is mapped to one or several partial resources in the setof partial resources.
 44. The method of claim 38 wherein the updating ofthe mapping is made using a recursive optimization algorithm forminimizing the total amount of wasted resources in view of the obtainedinformation and the set of service requirements.
 45. The method of claim38 wherein the updating of the mapping is made when the obtainedinformation indicates that at least one traffic characteristic of atleast one service level aggregate flow has changed by a predeterminedamount since the last update of the mapping.
 46. A control unit forcontrolling the mapping of service level aggregate flows oftelecommunications traffic to a set of partial resources for forwardingtraffic in a network, wherein each service level aggregate flowcorresponds to a service level associated with a set of servicerequirements, wherein the control unit comprises means for receivinginformation regarding traffic characteristics of each service levelaggregate flow and the performance of the set of partial resources meansfor dynamically controlling the mapping of the service level aggregateflows to the set of partial resources, based on said receivedinformation, to obtain an updated mapping that reduces the total amountof wasted resources, while fulfilling the service requirements of theservice levels, wherein the control unit further comprises means fordynamically controlling resource parameters governing the performance ofthe set of partial resources to achieve the combination of mapping andresource parameters that minimizes the total amount of wasted resources,while fulfilling the service requirements of the service levels.
 47. Thecontrol unit of claim 46 wherein said resource parameters are schedulingparameters governing how the set of partial resources are multiplexed ona physical link.
 48. The control unit of claim 46 wherein the controlunit further comprises means for sending information regarding thecurrent mapping to an admission control unit which controls theadmission of microflows into the service level aggregate flows.
 49. Thecontrol unit of claim 46 wherein said information regarding theperformance of the set of partial resources includes information aboutpacket delay and packet loss of each partial resource.
 50. The controlunit of claim 46 wherein said information regarding trafficcharacteristics of each service level aggregate flow includesinformation about mean rate and peak rate.
 51. The control unit of claim46 wherein said means for dynamically controlling the mapping isarranged to control the mapping such that each service level aggregateflow is mapped to one or several partial resources in the set of partialresources.
 52. The control unit of claim 46 wherein said means fordynamically controlling the mapping includes computation means arrangedto use a recursive optimization algorithm for minimizing the totalamount of wasted resources in view of said received information and theset of service requirements.
 53. The control unit of claim 46 whereinthe control unit is arranged to update the mapping when the receivedinformation indicates that at least one traffic characteristic of atleast one service level aggregate flow has changed by a predeterminedamount since the last update of the mapping.